The invention is based on a valve assembly as set forth hereinafter.
From U.S. Pat. No. 3,989,063, a valve assembly suitable for an anti-skid brake system is known, which includes two valves, actuatable in succession, having valve seats and valve balls, and which has an electromagnet having an armature and at least one restoring spring engaging it and at least one barrier spring. By subjecting a coil of the electromagnet to two current intensities of different levels, it is possible to close a so-called master cylinder connection of the valve assembly and thereby disconnect it from a wheel brake connection, or to connect this wheel brake connection to a pressure relief connection. A pressure prevailing at the wheel brake connection may for example be kept constant, even if a higher pressure prevails at the master cylinder connection, for example because of a more forceful actuation of the brake pedal. If the maintenance of constant pressure in the wheel brake connection is terminated by switchover of the valve assembly, so that the pressure prevailing in the master cylinder connection is propagated unhindered in the wheel brake connection, then disadvantageously rapid rises of brake pressure may sometimes occur in the associated wheel brake, which can lead to disadvantageously severe overbraking of an associated wheel.
In a brake system known from U.S. Pat. No. 4,141,595 (FIG. 2), to avoid disadvantageously rapid brake pressure increases in the anti-skid situation, a valve assembly having a built-in throttle has been provided. This throttle, which is operative in a particular switching position of the valve assembly, disadvantageously hinders rapid brake pressure increases after brake pressure reductions that were performed for the sake of skid prevention. U.S. Pat. No. 4,141,595 does not disclose any constructive details for practical embodiment of a valve assembly with a built-in throttle.